Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size, configuration and capacity of wind turbines. One such modification has been to include a wingtip device, such as a winglet, at the tip of each wind turbine rotor blade. Generally, winglets can be employed to improve the overall efficiency and performance of a wind turbine. For example, a winglet may decrease the amount of spanwise flow generated at the tip of a rotor blade and, thereby, reduce drag on the rotor blade. Winglets may also be installed on rotor blades to reduce the overall diameter of the wind turbine as well as to reduce noise emitted by the blades. Further, winglets may also provide an increase in the power coefficient of a wind turbine and, thus, reduce the cost of energy generated by the wind turbine.
While the various performance advantages, described above, can be provided to a wind turbine by both winglets extending away from the wind turbine tower (i.e., pressure side winglets) and winglets extending towards the tower (i.e., suction side winglets), it is generally understood that the greatest performance advantages can provided by a suction side winglet. However, for wind turbines having rotors upwind of the tower, suction side winglets can be very problematic. Specifically, installing a suction side winglet on a conventional rotor blade reduces the distance between the tip of the rotor blade and the tower. Such a reduction in tower clearance can dramatically increase the risk of one or more of the rotor blades striking the tower. When a tower strike occurs, the rotor blade and the tower can be significantly damaged and, in some instances, a tower strike can even bring down the entire wind turbine. Thus, tower strikes are very costly and require considerable downtime to repair or replace damaged components.
Accordingly, there is a need for a rotor blade that can accommodate a suction side winglet without increasing the likelihood of the rotor blade striking the tower.